[common] Remove unused member in KeyEncoderTraits

Change-Id: Ia36fd64f9c9219f7ab16dd264a49bccab31aaca6
Reviewed-on: http://gerrit.cloudera.org:8080/14506
Tested-by: Kudu Jenkins
Reviewed-by: Adar Dembo <adar@cloudera.com>
1 file changed